Desquamative interstitial pneumonia (DIP), respiratory bronchiolitis-associated interstitial lung disease (RB-ILD) and idiopathic pulmonary fibrosis (IPF) are the interstitial lung diseases of unknown etiology. Among patients with these disorders there is a prevalence of current or ex-smokers: over 90% in RB-ILD, 60-90% in DIP and 41-83% in IPF. Thus, cigarette smoking is to be a risk factor of a great significance. In clinical practice a correct differential diagnosis between RB-ILD and DIP on one hand and IPF on the other one is very important. Both bronchoalveolar lavage fluid and lung biopsy specimen taken from RB-ILD and DIP patients contain increased proportion of dusty brown alveolar macrophages. On CT scans the extent of fibrosis and inflammation areas is rather low. Contrary to IPF the prognosis of RB-ILD and DIP is generally good. Most patients improve clinically and radiologically with smoking cessation and corticosteroids. Further attempts towards new facts regarding the relationship between cigarette smoking and the pathogenesis and clinical course of different types of interstitial lung diseases are still needed.